The present invention relates to cosmetic compositions containing a novel thickening system of aqueous media based on associative polyurethanes and fatty chain nonionic polymers, as well as to their use in particular as leave-in haircare gels or styling gels.
The thickening and/or gelation of aqueous media with polymers has been an important subject of cosmetic research for a long time. The production of an advantageous thickening effect with a water-soluble polymer generally assumes a high molar mass and a large hydrodynamic volume. The gelation of an aqueous medium is then considered as being the result of a three-dimensional polymer network obtained by crosslinking linear polymers or by copolymerizing bifunctional and polyfunctional monomers. However, the use of such polymers of very high molar mass poses a certain number of problems, such as the relatively unpleasant texture and the difficulty in spreading the gels obtained.
One advantageous approach consists in using, as thickeners, polymers capable of reversibly self-associating or of associating with other molecules or particles. This physical association gives rise to thixotropic or rheofluidizing macromolecular systems, i.e. systems whose viscosity depends on the shear forces to which they are subjected.
Such polymers capable of reversibly self-associating or of associating with other molecules are known as xe2x80x9cassociative polymersxe2x80x9d. The forces of interaction in play can be very different in nature, for example of electrostatic nature, of hydrogen bonding type or hydrophobic interactions.
One specific case of associative polymers is amphiphilic polymers, i.e. polymers comprising one or more hydrophilic portions which make them soluble in water, and one or more hydrophobic zones via which the polymers interact and self-assemble or assemble with other molecules.
It is known practice to prepare hair compositions in gel form using, as thickening system, such associative amphiphilic polymers, in combination with surfactants. It is thought that the advantageous rheological properties of the gels thus obtained are due to the formation of mixed micelles containing the surfactants and the hydrophobic portions of the amphiphilic polymers, these micelles constituting a multitude of physical crosslinking points.
However, these compositions based on associative polymers and surfactants do not always have the desired cosmetic properties. Thus, the presence of surfactants, even in small amounts, can bring about an undesirable change in the cosmetic properties of the said compositions, such as the properties of application or of feel after drying. Moreover, in particular in the sector of leave-in haircare or styling gels, it is important to be able to distribute the product uniformly over the entire head of hair so as to avoid excessive loads and the cosmetic defects resulting therefrom.
It has now been discovered that it is possible to obtain a good thickening, or even gelling, effect and advantageous cosmetic properties by combining associative nonionic polyurethanes with nonionic polymers comprising at least one unit containing a fatty chain.
The gel obtained by the combination of these two types of polymer has a very melting texture and is pleasant to apply. The final feel on dried hair is more pleasant and less laden. The gel moreover has excellent styling power.
One subject of the present invention is thus a cosmetic composition comprising at least one associative nonionic polyurethane in combination with at least one nonionic polymer comprising at least one unit containing a fatty chain.
Another subject of the present invention is the use of the combination of at least associative nonionic polyurethane and at least one nonionic polymer comprising at least one unit containing a fatty chain as a thickening system for cosmetic compositions.
A third subject of the invention is a cosmetic process for treating the hair using a cosmetic composition obtained by combining at least one nonionic associative polyurethane and at least one nonionic polymer comprising at least one unit containing a fatty chain.
Other subjects will become apparent on reading the description and the examples which follow.
The cosmetic compositions in accordance with the invention are essentially characterized in that they contain, in a cosmetically acceptable medium,
(A) at least one amphiphilic nonionic associative polyurethane corresponding to the general formula 
in which
at least one of the residues R1 and R2 represents a C8-C18 higher alkyl group and the other, where appropriate, represents a C1-C6 lower alkyl group,
R3 represents a C4-C36, preferably C6-C10, hydrocarbon-based radical,
R4 represents a hydrogen atom or a C1-C6 alkyl radical, preferably a hydrogen atom,
a ranges, independently, from 90 to 600, and
b is from 1 to 4, and
(B) at least one nonionic polymer comprising at least one unit containing a fatty chain and which is other than the polyurethane of formula (I).
According to the invention, the expression xe2x80x9cC1-C6 lower alkyl groupxe2x80x9d means an alkyl group containing a linear or branched chain comprising from 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, n-pentyl and n-hexyl radicals, as well as the corresponding branched isomers.
In accordance with the invention, the C8-C18 higher alkyl groups denote alkyl groups containing a linear or branched chain comprising from 8 to 18 carbon atoms, such as octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and octadecyl radicals.
In one preferred embodiment, only one of the xcex1,xcfx89-alkyl radicals R1 and R2 of the polymer of formula (I) represents a C8-C18 higher alkyl group and the other represents a C1-C6 lower alkyl group.
A particularly recommended associative polyurethane of the present invention is that in which one of the groups R1 and R2 represents an octadecyl radical and the other represents a methyl group.
The associative polyurethanes used in the compositions of the present invention are used in the form of an aqueous solution or suspension optionally containing a certain amount of soluble starch. This starch can be any starch extracted from natural sources, such as wheat starch, cornstarch, rice starch, potato starch, etc. and which has been chemically, enzymatically or microbiologically modified so as to be soluble in water.
A preferred polymer is sold by the company Rohm and Haas under the name Acrysol 46. It is a polyurethane obtained by condensation of hexamethylene diisocyanate and polyethylene glycol, and bearing, on average, a methyl residue and an octadecyl residue at its ends, respectively. This polymer is in the form of an aqueous solution containing 15% by weight of polyurethane active material also containing 3-5% of an enzymatically modified starch matrix.
According to the present invention, the nonionic polymers comprising at least one fatty chain, which are used as component (B), are preferably chosen from:
(1) celluloses modified with groups comprising at least one C8-22 fatty chain, for example
hydroxyethylcellulose modified with groups comprising at least one C8-22 fatty chain. Such a product is, for example, Natrosol Plus Grade 330 (C16 alkyl chains), sold by the company Aqualon, or Bermocoll EHM 100 sold by the company Berol Nobel; or
celluloses modified with alkylphenyl polyalkylene glycol ether groups, such as the product Amercell Polymer(copyright) HM-1500 sold by the company Amerchol;
(2) hydroxypropyl guars modified with groups comprising at least one C8-22 fatty chain, such as the product Esaflor(copyright) HM 22 sold by the company Lamberti, and the products Miracare(copyright) XC95-3 and RE205-1 sold by the company Rhxc3x4ne-Poulenc;
(3) copolymers of vinylpyrrolidone and of hydrophobic monomers containing a C8-22 fatty chain, such as, for example, the products Antaron(copyright) V216, Antaron(copyright) V220, Ganex(copyright) V261 and Ganex(copyright) V220, sold by the company I.S.P.;
(4) copolymers of C1-6 alkyl methacrylates or acrylates and of amphiphilic monomers comprising at least one C8-22 fatty chain, such as, for example, the oxyethylenated methyl methacrylate/stearyl acrylate copolymer sold by the company Goldschmidt under the name Antil(copyright) 208;
(5) copolymers of hydrophilic methacrylates or acrylates and of hydrophobic monomers comprising at least one C8-22 fatty chain, such as, for example, a copolymer of polyethylene glycol methacrylate and of lauryl methacrylate, such as the product 470/66 sold by the company National Starch;
(6) polyurethanes comprising at least one unit containing a fatty chain, which are other than the polyurethanes of formula (I).
According to the invention, the associative polyurethanes and the nonionic polymers containing fatty chains are used in amounts which are sufficient to obtain satisfactory thickening or gelation of the aqueous medium.
An amount of associative polyurethanes of between 0.1 and 10% by weight and preferably between 0.5 and 5% by weight, expressed as active material and relative to the total weight of the composition, is recommended in particular.
In the compositions of the present invention, the nonionic polymers comprising at least one unit containing a fatty chain are present in a proportion of from 0.01 to 10% by weight, preferably in a proportion of from 0.1 to 5% by weight, of active material relative to the total weight of the composition.
In the present invention, the ratio of the said nonionic associative polyurethane (A) of formula (I) to the said nonionic polymer comprising at least one unit containing a fatty chain (B) is preferably within the range from 90/10 to 10/90.
The cosmetically acceptable medium preferably consists of water and can also contain cosmetically acceptable solvents, for example lower monoalcohols such as ethanol or isopropanol, glycols such as ethylene glycol, glycol ethers such as the alkyl ethers of ethylene glycol or of diethylene glycol, or alternatively fatty acid esters, all of these solvents being used alone or in the form of a mixture.
The haircare or styling gels can also contain one or more additives usually used in such hair compositions. Mention may be made, for example, of fragrances, dyes, preserving agents, sunscreens, vitamins, pH regulators, etc. It is clearly understood that the choice of these compounds should take into account possible interactions with the thickening system. A person skilled in the art will take care to ensure that the addition of these additives will not have an unfavourable influence on the advantageous properties of the compositions obtained by means of the present invention.
One preferred cosmetic process for treating the hair, according to the invention, consists in applying and homogeneously distributing the compositions defined above on the hair and in drying the hair thus treated without rinsing it.
The examples which follow are intended to illustrate the invention without thereby being limiting in nature.